Several behavioral effects of abused drugs, particularly their reinforcing effects, are altered when experimental subjects are deprived of food. The research proposed here is designed to extend research into fundamental relationships between levels of food deprivation and the behavioral effects of the abused drugs cocaine and morphine. Several of the experiments will determine whether food deprivation alters the suppressive effects of cumulative doses of cocaine or morphine on operant (i.e., rewarded) behavior maintained by different reinforcers. Combinations of different levels of food deprivation and doses of drugs will be tested in rats lever-pressing under comparable schedules of food and water reinforcement, and shock avoidance. The effects of a neurochemical consequence of feeding will also be tested by administering drugs in combination with the potent endogenous feeding-inducing peptide, neuropeptide Y. These studies will have general implications for the role nutritional variables play in drug abuse, as well as provide the basis for research on the manner in which behavioral variables influence the nature of drug interactions.